The present invention relates to high speed, high-density electronic equipment. More specifically, this invention relates to a midplane board featuring surface contact connectors.
In recent years, the field of electronics has generally been characterized by a certain effervescence. In fact, ever-increasing consumer demands, research and development, and greater competition in the market place are all factors that are contributing to numerous innovations in this field. Architects of the next generation IP networks are therefore demanding exponentially higher system throughputs to sustain network traffic growth. However, this involves the use of high density, high-speed equipment and one of the key issues associated with this particular type of equipment pertains to the level of connectivity required between various electrical components such as circuit boards. More specifically, switching systems are required to properly direct different communication channels from an origin to a destination.
A method commonly used to interconnect a multitude of circuit boards carrying communication channels is backplane structures. In such structures, a backplane is placed at one end of an electronic equipment shelf and has a surface that receives a plurality of circuit boards. The circuit boards are oriented such that they are substantially parallel to one another. Generally, the backplane is located at the rear of the electronic equipment shelf, hence the term  less than  less than backplane greater than  greater than .
A deficiency associated with backplane structures pertains to the level of connectivity required. Backplanes, as stated previously, have a single interconnection surface that receives circuit boards. As a result, only a limited number of circuit boards can be coupled to the backplane. In contemporary systems however, ever-increasing network traffic implies that numerous communication channels, and hence circuit boards, are necessary to achieve the required level of connectivity within a communication system.
Another traditional method uses a midplane board in conjunction with pin and box connectors. Such a midplane board is disclosed in U.S. Pat. No. 5,887,158 (Sample et al.) assigned to the Quickturn Design Systems, Inc. corporation. The content of this document is hereby incorporated by reference. The use of a midplane board is advantageous since it accommodates two sets of circuit boards arranged on either side of the midplane board. More specifically, the first surface of the midplane board is provided with a plurality of connector pins that engage corresponding sockets formed on the circuit connecting on the first surface. The opposite (second) surface of the midplane board also has connector pins that also engage sockets formed on circuit boards connecting on the second surface. The circuit boards connecting with the first surface are oriented in a direction that is either parallel or orthogonal to the circuit boards connecting with the second surface. When the connector pins of circuit boards positioned on opposite sides of the midplane board register at common junctions, holes, more commonly known as the xe2x80x9cthrough holexe2x80x9d, are drilled in the midplane in such a manner as to accommodate a single connector pin that traverses the midplane and thereby directly connects electrically both circuit boards.
Although the use of a midplane structure such as that described hereinabove is advantageous when compared to a more traditional backplane structure, it is not without its deficiencies. One of the disadvantages associated with the use of a through hole is the large space that each connector pin occupies. Thus, each connector requires a significant amount of midplane board space and this implies that the density of the connector pins is less than ideal. Moreover, another disadvantage in using through holes resides in the lack of freedom for the arrangement and positioning of the connector pins since the connector pins on both sides of the midplane board must register with one another to create the  less than  less than through holes greater than  greater than .
Consequently, there is a need in the industry for providing an improved midplane board that overcomes at least in part the deficiencies of the prior art.
In accordance with a first broad aspect, the invention provides a midplane board for use in an electronic equipment shelf. The midplane board has two main opposite surfaces, namely a first surface and a second surface. The first surface comprises a plurality of contact elements adapted to engage corresponding contact elements on a first circuit board. The second surface comprises a plurality of contact elements adapted to engage corresponding contact elements on a second circuit board. At least one signal connection path is formed in the midplane board between a contact element on the first surface and a contact element on the second surface. The contact elements on the first surface are geometrically located with relation to the contact elements on the second surface in such a way that at least a portion of a side of the first circuit board (when connected with the first surface) will be opposed to at least a portion of a side of the second circuit board (when connected with the second surface). When at least a portion of a side of the first circuit board is opposed to at least a portion of a side of the second circuit board the two circuit boards are said to xe2x80x9cintersectxe2x80x9d one another. In this specification, xe2x80x9cintersectxe2x80x9d means that when an observer faces one of the main surfaces of the midplane, the observer will see both circuit boards cut-through one another. The condition of intersection is met irrespective of the angle at which the circuit boards cut one another. The angle may be anywhere from 90xc2x0 to 0xc2x0.
The contact elements on the midplane are surface contact elements and form, with the corresponding contact elements on a circuit board, a surface electrical connector. This electrical connector is distinguished from a male/female type connector that is characterized by the presence of a pin that penetrates a socket. In the case of a surface electrical connector, at least the contact element on the midplane board is substantially flat.
The use of surface electrical connectors to establish an electrical connection between the midplane and a circuit board is advantageous because it no longer requires a precise registration between circuit boards on opposite sides of the midplane, as in the case of the xe2x80x9cthrough holexe2x80x9d technology. With the present invention, the contact elements on one main surface of the midplane do not have to precisely match the location of the contact elements on the other main surface in order for them to be electrically connected. This added level of flexibility can be exploited to yield advantages such as increasing the connection density, among others.
In accordance with yet another broad aspect, the invention provides a midplane board comprising first and second surfaces. Each surface, which is in opposite relationship with the other, features a plurality of contact elements. The midplane board comprises at least one intersect area that is characterized by a plurality of signal connection paths that are operative for establishing connections between the contact elements on both surfaces.
In a specific example of implementation, the plurality of signal connection paths defines a certain pattern tile that is symmetrical along first and second axes. The pattern tile is reproduced along the length and width of the midplane board and a plurality of intersect areas can thus be provided.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.